Crop sensitivity to herbicides.

For over 30 years, the Ontario Agriculture Colleges (OAC) “weed’s team” has competed in the Collegiate Weed Science Competition organized by the North Eastern Weed Science Society. In preparation for the “herbicide identification” portion of the competition, each year an area at the Elora Research Station is planted to a number of different crop and weed species and then sprayed with several herbicides.

This training plot also serves as a screening tool to look for potential new herbicide options in crops that perhaps don’t get a lot of attention  (e.g. forages). It also gives insight into how sensitive a crop might be to an off-target herbicide drift event or tank contamination.

When I’ve been able to go through this training trial in detail, I will assess the level of crop injury caused by each herbicide on a scale of 0 to 100% where 0% means “no observed affect” and 100% means “dead”. This is typically done at 3-4 weeks after application. Now that multiple years of evaluations exist, I’ve decided to publish these ratings here, with the primary objective being as a training resource for students competing in the “OAC weed’s team”. A secondary objective may be to provide manufacturers and commodity organizations with a starting point to perhaps explore and pursue new production registrations.

This will serve as a landing page for summaries of responses to different herbicides applied prior to (PRE) and after (POST) crop emergence.

Special thanks goes to Peter Smith at the University of Guelph, who has maintained these trials every year, and Dr. Tardif for spearheading this initiative. 

IMPORTANT: It is a violation of the Pest Control Products Act to use a pesticide in any way that is inconsistent with the directions on the label. Always read and follow the directions on the pesticide label before using. 

LIMITATIONS: This trial is conducted annually, but only at one location and one soil type. Crop sensitivity to herbicides is influenced by a number of factors, such as soil texture, organic matter, pH, environmental conditions and stresses. Therefore, the confidence that the observations provided below will be seen in all soil types and environments is very low. 

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Buckwheat sensitivity to PRE herbicides (2024)

Herbicide Tradename	active ingredient	# of trials	Average Injury (%)	Lowest Injury (%)	Highest Injury (%)
Aatrex 480	atrazine	3	57	0	100
Xtendimax	dicamba	3	53	50	60
Sencor 75 DF	metribuzin	2	50	10	90
Converge Flexx	isoxaflutole	1	50	50	50
Pursuit	imazethapyr	3	43	0	80
Classic	chlorimuron-ethyl	3	43	10	90
Reflex	fomesafen	2	35	20	50
Prowl H2O	pendimethalin	2	25	0	50
Permit	halosulfuron	3	20	0	50
Zidua SC	pyroxasulfone	2	10	0	20
Armezone	topramezone	2	10	0	20
Callisto	mesotrione	2	5	0	10
Valtera	flumioxazin	3	3	0	10
Dual II Magnum	s-metolachlor	3	3	0	10
Command	clomazone	2	0	0	0
FirstRate	cloransulam-methyl	1	0	0	0
2,4-D Ester 700	2,4-D	2	0	0	0
Eragon LQ	saflufenacil	2	0	0	0

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• Annual rye grass (Lolium multiflorum)
• Crimson clover (Trifolium incarnatum)